MARINE ANIMALS ON SUBMERGED METALS. 



couple, Al and Sn, the Al member carried only Botryllus and 

 Bugnla, though these were present in considerable amounts. This 

 limitation may have been due to poisonous Sn ions which appar- 

 ently checked growth in another instance to be referred to later 

 (Fe). 



The second metal to be considered is Zn. This stands below Al 

 in the electromotive series, but above Fe, Sn, Pb, and Cu. When 

 combined with Al, it remained uncorroded in seawater (Table III. 

 and Plate II.). With Fe and Sn it corroded slightly and with Pb 

 and Cu much more. A small amount of Bugula grew on it when 

 it was combined with Al, where it must have been relatively in- 

 active. In all other combinations animals were absent probably 

 because its activity resulted in the formation of an abundance of 

 Zn ions or soluble Zn compounds. 



TABLE III. 



COUPLES BETWEEN ZN AND THE FlVE OTHER METALS, ONE OF WHICH. AL. 



STANDS ABOVE ZN, AND FOUR OF WHICH, FE, SN, PB, AND Cu, STAND 



BELOW ZN IN THE ELECTROMOTIVE SERIES. 



The animals are indicated as in Table I. 



The third metal is Fe, which stands below Al and Zn and above 

 Sn, Pb, and Cu in the electromotive series. When combined with 

 Al and with Zn, it was not much acted on by seawater (Table IV.), 

 but in combination with Sn, Pb, and Cu it rusted freely. 



TABLE IV. 



COUPLES BETWEEN FE AND THE FlVE OTHER METALS, TWO OF WHICH, AL AND 



Zx, STAND ABOVE FE, AND THREE OF WHICH, SN, PB, AND Cu, STAND 



BELOW FE IN THE ELECTROMOTIVE SERIES. 



The animals are indicated as in Table I. 



